Assign event listener from js class

Question

I want to assign onclick event listener to an object from within a class and then get some variable from the instance that created that onclick

function myclass() {

    this.myvar;

    this.myfunc = function() 
    {
        alert(this.myvar);
        document.onmousedown = this.mouseDown;        
    }

    this.mouseDown = function(e) 
    {
        alert(this.myvar); //does not work of course
        //how could I access myvar from current myclass instance
    }

}


var myclass_instance = new myclass();
    myclass_instance.myvar = 'value'
    myclass_instance.myfunc();

http://jsfiddle.net/E7wK4/

What is it not doing that you expected it to do?

mplungjan
– mplungjan

2013-07-22 17:54:05 +00:00
Commented Jul 22, 2013 at 17:54 — mplungjan
– mplungjan, Commented Jul 22, 2013 at 17:54

Naftali · Accepted Answer · 2013-07-22 17:55:43Z

1

this in the mouseDown event is not the this of the instance.

Try this instead:

function myclass() {

    var _this = this;

    this.myvar;

    this.myfunc = function() 
    {
        alert(this.myvar);
        document.onmousedown = this.mouseDown;        
    }

    this.mouseDown = function(e) 
    {
        alert(_this.myvar); //<<<<
    }

}

Demo: http://jsfiddle.net/maniator/E7wK4/1/

answered Jul 22, 2013 at 17:55

Naftali

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Comments

Evan Borden · Accepted Answer · 2013-07-22 17:57:33Z

1

As an alternative to @Neal you could bind this.

document.onmousedown = this.mouseDown.bind(this);

answered Jul 22, 2013 at 17:57

Evan Borden

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